The size and weight of the fly determines what size tippet works best with that fly. A 3wt rod is for smaller flies and the leader will have a lighter tippet. If you were fishing a size 16 fly a 5X tippet would be used. If you were fishing an 8wt rod with a size 6 fly, a size 2X tippet would be called for. The companies making the leaders size the butt of the leader to match a group of fly lines it might be used on. All you have to worry about is what size tippet you will be using for a particular sized fly.

Tippet Diameter

Tippet Size

Pound Test

Fly Size

.003

8x

1.2

24-26-28

.004

7x

2

20-22-24-26

.005

6x

3

16-18-20-22

.006

5x

4

14-16-18

.007

4x

5

12-14-16

.008

3x

6

10-12-14

.009

2x

7

6-8-10

.010

1x

8.5

2-4-6

.011

0x

10

1/0-2-4

.012

x1

12

2/0-1/0-2

.013

x2

14

3/0-2/0-1/0-2

.014

x3

16

5/0-4/0-3/0-2/0

.015

x4

18

6/0-5/0-4/0-3/0

NOTE: Leader diameters and strengths vary from manufacture to manufacture and with different materials or processes.

Here is a quick way to calculate the best size tippet to use on the water. You take the fly size and divide it by 4 and then add 1. For example, take a size 6 hook, divide 6 by 4 and you get one. Add one to that and you get 2. So for a size 6 hook use a 2X leader. You will note that the chart says 1X or 2X will work. The formula is a guide to get you close to the proper sized tippet on the water. In this case you use the leader that is most appropriate for the size of the fish.